The above described type connection is commonly known as a "fused" connection. The required function of predictable failure of the connection is usually accomplished by the shearing of a single shear pin of known load capacity which is located and oriented in such a manner as to provide the only load path between a loaded structure and a structure which will react such load.
A new and unique problem is presented, for which a conventional solution is unsatisfactory, when the load reaction structure is incapable of carrying an equal amount of maximum load in all directions. For example, a given load reaction structure may be capable of reacting a much larger force in a first (e.g. horizontal) direction than in a second (e.g. vertical) direction. The problem is that a conventional single shear pin connection knows no direction. That is, it has only one failure level and it will always fail at that level regardless of the direction of the overload. Thus, a single shear pin type fused connection is not a suitable solution for a fused joint when:
(1) Applied loads are of varied direction and magnitude with respect to the joint or pin axis.
(2) The load capacity of the reaction structure is not equal to the highest magnitude of the applied load in all directions.
(3) It is desirable or necessary to protect the load reaction structure from overload in directions of minimum capacity.
This problem has been encountered in aircraft design, at a connection between a landing gear support beam (loaded structure) and a wing frame (reaction structure). The wing frame is capable of reacting a much larger load in the horizontal direction than it is in the vertical direction.
The primary requirements of a fused connection between the main landing gear support beam and the wing of a particular new aircraft being built by The Boeing Company are:
1. a single pin attachment is required,
2. a clear and predictable break away of the joint is required with overload application in either the horizontal or vertical direction,
3. the applied loads which must be safely carried are approximately twice as large in the horizontal direction as those in the vertical direction,
4. the capacity of the supporting wing structure to react a load in the vertical direction is approximately one half of the support structure capability in the horizontal direction.
The fused single pin connection of the present invention meets these requirements.